Step 3: Combine the Gelatin and Sugar Syrup

1. Once the sugar syrup has reached 240°F, remove the saucepan from the heat.
2. Add the bloomed gelatin mixture to the syrup, stirring gently until the gelatin has completely dissolved and the mixture is smooth.

Step 4: Whip the Marshmallow Mixture

1. Pour the syrup into the bowl of a stand mixer (or use a hand mixer). Let it cool for about 5 minutes.
2. Add the vanilla extract to the mixture.
3. Using the whisk attachment, start mixing on low speed and gradually increase to medium-high. Whip the mixture for about 10-12 minutes, or until it becomes thick, fluffy, and white. You’ll know it’s ready when it holds stiff peaks.

Step 5: Transfer to the Pan

1. While the marshmallow mixture is whipping, prepare your baking pan by lightly greasing it with cooking spray or oil. Then, dust the bottom and sides of the pan with a mixture of powdered sugar and cornstarch (this prevents the marshmallows from sticking).
2. Once the marshmallow mixture is whipped to stiff peaks, use a silicone spatula to transfer it into the prepared pan. Smooth the top to make it even.

Step 6: Let It Set

1. Dust the top of the marshmallow mixture with more powdered sugar and cornstarch to prevent sticking.
2. Cover the pan with a clean kitchen towel and let it sit at room temperature for at least 4 hours, or until the marshmallows are fully set. For best results, leave them overnight.